1. Field of the Invention
The inventions disclosed herein are in the field of dental instruments. More particularly, the inventions relates to dental matrix bands which are positioned around a dental preparation to act as a form for the material used to fill the preparation. The inventions also relate to the use of such bands in band holders as well as the related methods.
2. Background Art
In the field of dentistry, dental practitioners often treat patients who have developed cavities on the side of a tooth. When these cavities are located adjacent to neighboring teeth they are known as interproximal cavities. In order to treat cavities on the sides of teeth such as interproximal cavities, the dental practitioner removes the infected portion of the tooth, then deposits a filling such as a resinous material or an amalgam into the tooth preparation.
In order to properly deposit the filling without undesired seepage of the filling material beyond the side of the tooth, typically a matrix band is disposed about the tooth, after which the filling material is deposited. A matrix band is typically a metallic or plastic strip having first and second ends which are joined, thereby forming a mold which is disposed about the tooth. When encircled about the tooth, the matrix band acts as a form, similar in function to a concrete form, providing a mold for the desired shape of the repaired tooth.
In order to maintain the matrix band in a desired position with respect to the tooth to be repaired, small dental wedges are often placed in the interproximal spaces between the matrix band and the teeth adjacent the tooth to be repaired. The wedges also space the teeth adjacent to the tooth to be repaired during the filling procedure. Dental wedges may be used to spread adjacent teeth for a variety of other purposes such as enabling a dental matrix band to be initially positioned around a tooth. Due to the elasticity of the periodontal fibers the teeth will resume their original position after the wedges and matrix bands are removed.
FIG. 1 depicts a tooth 10 encircled by a dental matrix band 20. A dental wedge 30 is shown being positioned between tooth 10 and adjacent tooth 12. Pliers 18 are used to hold wedge 30. FIG. 2 shows a typical matrix band at 20 before being placed around a tooth. FIG. 3 shows dental wedge 30 in more detail.
Matrix bands are sold having many different shapes, thickness and properties. For example, different matrix bands are sold for use with molars, premolars or bicuspids, etc. of adults as well as specialized pediatric matrix bands. One of the commonly used matrix band configurations is known as the Tofflemire-type matrix band, such as is shown in FIG. 2. Tofflemire-type matrix bands are elongated strips which are slightly curved or arched such that the bands are shaped somewhat like a boomerang. Matrix bands are also available which are straight and can therefore be sold in spools. Many matrix bands also have a lip or cervical extension to assist in placing the band past the cervical margin.
The matrix bands have any suitable thickness to fit between teeth. However, typical thickness are 0.03 mm, 0.035 mm, 0.038 mm, 0.045, and 0.05 mm. Generally, contact is optimized by using the thinnest matrix band possible especially when polymerization of a composite is required. Some matrix bands are sold which have regions, known as contact areas, which are much thinner than the remainder of the matrix band. For example, the contact area may be 0.0127 mm (0.0005 inches thick) while the remainder is 0.03 mm thick or greater. Such matrix bands are particularly useful with Class II restorations.
The matrix bands can also be formed from different materials to yield different properties. Traditionally, matrix bands have been prepared from stainless steel. Bands can be designed to be adequately soft to allow them to be individually shaped by finger pressure or by an instrument while others are more rigid. Such properties can be achieved by varying the thickness or the composition of the band. Increasing amounts of matrix bands are being sold which are transparent or translucent to enable radiant energy to pass through the band toward composite material in a preparation to polymerize the composite material. Such bands may be integrally formed from a single material such as polyester or Mylar.TM. sold by DuPont. Additionally, bands are sold with portions formed from translucent plastic and other portions which are formed from stainless steel. One of the advantages of matrix bands formed from both stainless steel and plastic is that the stainless steel can pass through tight contact points which are sometimes difficult for some plastics.
Many matrix band designs have been produced to achieve various objectives. For example, U.S. Pat. No. 4,563,152 discloses the ability to use a matrix band to replace a narrow sand paper strip used to remove "flash" which forms due to overfilling a tooth with a polymerizable composite material. It was observed that the sanding strip was generally thicker than the matrix band so it was difficult to insert and successfully use the sanding strip. The solution to this problem disclosed in U.S. Pat. No. 4,563,152 is the use of a matrix band which has a portion on the side which faces the preparation which is configured to abrade the flash and other excess cured material that has escaped the cavity preparation. This enabled the matrix band to be used for its conventional purpose and also to abrade the restorative material from the mesial surface of the restored tooth without having to remove the band and insert the sanding strip.
A significant problem with the use of conventional matrix bands and dental wedges is the tendency of the dental wedges to slip out their positions in the interproximal spaces. When the wedges slip out from between the teeth, the desired configuration of the restored tooth may be distorted. Another problem related to the interface between wedges and dental matrix bands is the potential for injurious slippage during insertion of a wedge. These problems are not solved by the prior art.
In addition to the prior art wedge shown in FIG. 3, FIGS. 4-5 depict other examples of prior art wedges respectively at 40 and 50 and are discussed hereinbelow. Typical wedges have a triangular cross section as shown. This triangular cross section includes a thin apex at the distal insertion end which widens into a flat base at the other end, the proximal gripping end. Each wedge in FIGS. 3-5 is depicted as having a distal insertion end, respectively shown at 32, 42 and 52 and a proximal gripping end, shown respectively at 34, 44 and 54.
As shown in FIG. 1, a wedge is typically placed with the widened end located toward the gum line and with the thin apex extending between the teeth and away from the gums in order to fit properly in an interproximal space. When using such dental wedges, the practioner is careful to orient the wider end toward the gumline while the more thinner, pointed apex is directed upward between the teeth.
In light of this triangular configuration of typical wedges, it is important to orient the wedge properly with respect to the interproximal space before pressing the body of the wedge, shown respectively in FIGS. 3-5 at 36, 46 and 56, into the interproximal space. In addition, the properly oriented wedge must be precisely guided into the space. However, it is often difficult to orient the wedges correctly within the desired interproximal space in the mouth due to their small size and the difficulty involved in controlling the insertion of the wedge without making the patient uncomfortable or possibly damaging the gums and/or teeth of the patient. Accordingly, a practioner maintains a solid grip on the wedge in order to strategically align and properly guide the wedge. Of course, it is also necessary for the practitioner to maintain a solid grip on the wedge to avoid dropping the wedge.
The tendency of these wedges to slip due to their shape is further increased due to their smoothness and relative rigidity when tightly gripped, particularly when covered with fluids, such as saliva or blood. Such smoothness and rigidity inherently result from the type of materials used to form conventional wedges. Typical dental wedges are comprised of a rigid plastic or wood, such as that from sycamore trees, having a smooth exterior surface which compounds the difficulties associated with firmly gripping the wedges due to their small size. Note that wedge 30 is formed from wood while wedge 40 is formed from a translucent plastic.
A practitioner typically uses small-nosed pliers, known as cotton pliers, to grip a particular wedge and to position the wedge within the mouth. To enhance a practioner's ability to grasp a wedge, some wedges have a head disposed on the proximal end of the body of the wedge. For example, wedges 40 and 50, are shown respectively with heads 48 and 58 attached to bodies 46 and 56. Head 48 has four gripping surfaces, 49a-d, which makes it easier to grasp than head 58. However, since head 48 is typically comprised of a rigid material, such as plastic, pliers still readily slip when contacting such wedges.
After the wedge is initially positioned, the dentist forces the wedge into final position. During the forced insertion, the likelihood of injury is greatest as the pliers or tweezers may slip off the wedge into the soft tissues in a patient's mouth. Additionally, when the dentist attempts to regrasp the wedge with cotton pliers there is also risk of slipping off the wedge. The slippery nature of the wedge can cause the wedge to be lost within the patients' mouth or ejected from the pliers across the room. Even if the small wedge is found, often it cannot be utilized due to the likelihood of contamination.
As indicated above, the slippery nature of wedges combined with the conditions in the oral cavity sometimes enable the wedges to become dislodged after being positioned in an interproximal space. The tendency to be displaced after being positioned may also result from being used in very tight interproximal spaces which makes it difficult to insert a sufficiently significant portion of the body of the wedge into the space.
There is, therefore, a need in the art for a matrix band which minimizes the tendency of wedges to be displaced from an interproximal spaces after being positioned therein such that the risk is reduced of impacting the desired shape of a restored tooth due to slippage.